Semiconductor devices having metal oxide layers of adjacent epitaxial p-type and n-type structures which form p-n junctions are known as semiconductor diodes, or p-n diodes, and are useful as light emitting diodes (LEDs) and power transistors. The further development of this technology has enabled their efficiency to rise exponentially, making them more widely useful in various applications. Among recent research trends are those that seek to reduce costs of producing semiconductor diodes, while enlarging the diode surface area and maintaining high performance and efficiency.
Generally, semiconductor diodes are manufactured using single crystal substrates of GaN, ZnO, Al2O3 (sapphire), SiC, SiO2 (quartz) and silicon. Large area substrates (e.g., greater than about 15.24 centimeters (cm) (6 inches)) of single crystal GaN and ZnO are not widely used due to their high cost, even though their lattice matching with p-type and n-type films is almost equal, which permits growth of superior quality single crystalline epitaxial films for making the best LEDs.
Silicon is known to be among the least costly of the suitable substrate materials, with high quality single crystal wafers having large surface area with about 20.32 cm (8 inches) to about 30.48 cm (12 inches) in diameter, or greater, available for deposition of metal oxide layers thereon. However, silicon substrates have their own drawbacks, including large lattice mismatch and increasing flexibility as their surface area increases, which hinders growth of high quality epitaxial layers of GaN, ZnO, or other oxides thereon, and subjects the deposited epitaxial layers to stress that increases the risk of fracture or other distortion of the crystal structures, respectively.
Many techniques have been developed to reduce the lattice mismatch, such as by first depositing MgO thin layers on the Si-based substrate, then growing an AlGaN layer, and finally depositing the GaN p- and n-type epitaxial layers. Still, there remain unacceptable degrees of defects in the quality of the epitaxial layers, which reduce the efficiency of semiconductor diodes produced this way.
Accordingly, it is desirable to provide semiconductor devices that use less expensive Si-based substrates for semiconductor diodes having epitaxial semiconductor layers made of GaN, notwithstanding the lattice mismatch between Si and GaN. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.